Notify the player if a picked block is already in their hotbar

mods/PLAYER/vl_pickblock/init.lua

@@ -1,3 +1,5 @@
+local S = minetest.get_translator("vl_pickblock")
+
 minetest.override_item("", {
 	on_place = function(itemstack, placer, pointed_thing)
 		if minetest.is_creative_enabled(placer:get_player_name()) then
@@ -21,6 +23,16 @@ minetest.override_item("", {
 				rnode = node
 			end
 
+			local inv = placer:get_inventory()
+			for i=1,placer:hud_get_hotbar_itemcount() do
+				local stack = inv:get_stack("main", i)
+				if stack:get_name() == rnode.name then
+					local msg = S("@1 is on slot @2", stack:get_short_description(), i)
+					mcl_title.set(placer, "actionbar", {text = msg, stay = 30})
+					return
+				end
+			end
+
 			return rnode
 		end
 	end

mods/PLAYER/vl_pickblock/locale/template.txt

@@ -0,0 +1,2 @@
+# textdomain: vl_pickblock
+@1 is on slot @2=

mods/PLAYER/vl_pickblock/mod.conf

@@ -1,3 +1,3 @@
 name = vl_pickblock
 description = Allows you to put the selected node in an empty slot of your hotbar when you're in creative mode.
-depeds = mcl_util
+depeds = mcl_util, mcl_title